A micro-fabricated potentiometric platform with application in a COVID-19 drug quantification and the determination of its binding affinity to a supramolecular host

Recent applications in host–guest chemistry include advanced sensing technologies, drug formulations, and drug delivery. Quantification of host–guest binding constants is significant to the continued optimization of their use. Binding constants offer valuable information about the stability and affinity of the formedcomplex that is essential to both drug formulations and delivery. In this study a novel green, portable, disposable, and cost-efficient microfabricated potentiometric sensor is introduced and successfully applied to determine the concentration of remdesivir (RMD), a COVID-19 drug, and its binding affinity to the supramolecular host sulfobutylether-β-cyclodextrin (SBEβCD) as a compatible solubilizing agent; to overcome the low water solubility of RMD which presents a significant challenge in its intravenous administration. The sensor incorporates multi-walled carbon nanotubes to improve stability and detection limits. To reduce interference effects and enhance the selectivity of the sensor for RMD, 4-tert-butyl-calix[8]arene was employed as an ionophore. A Nernstian potentiometric response for RMD over a concentration range of 1.0 × 10−3 to 1.0 × 10−6 M with a slope of 58.2 ± 0.9 mV decade−1 and a detection limit of 0.23 µM were achieved. The binding constant of the RMD-SBEβCD complex was determined to be 9.76 × 103 M−1. The proposed sensor was shown to be effective for drug quantification and measurements of binding affinities, providing valuable insights into the physicochemical properties of target drugs.